Enhanced system and method for string-balancing
Apparatuses and methods for configuring and managing solar panels to form strings of photovoltaic energy generators with improved performance and reduced cost. The photovoltaic energy generators are connected via one or more combined local management units (CLMUs), each having a plurality of direct current converters connected to and configured to receive direct current power from a respective solar panel. A controller unit shared by the CLMU's direct current converters is utilized to separately control the operation of each converter such that the power extracted from the solar panels is maximized. A communications unit coupled with the controller unit is utilized to facilitate communications between the controller unit and a system unit remote from the CLMU to report measurements and receive control signals.
1. A photovoltaic system, comprising:
a plurality of photovoltaic panels connected in a plurality of strings;
a bus; and
a plurality of converters for the plurality of strings respectively, each respective converter of the plurality of converters having a direct current input and a direct current output, each respective string of the plurality of strings connected to the bus via the respective converter and having a string output resulting from a series connection of photovoltaic panels, wherein:
the string output of the respective string is connected to the direct current input of the respective converter to generate the direct current output;
the string output of the respective string is connected in series with the direct current output of the respective converter to power the bus; and
the respective converter is configured to match
a voltage of a series connection of the string output of the respective string and the direct current output of the respective converter with
a highest voltage of string outputs in the plurality of strings.
2. The system of claim 1 , wherein at least one converter connected with at least one string having the string output that is equal to the highest voltage operates in a bypass mode.
3. The system of claim 1 , wherein the respective converter includes a bypass switch configured to connect the string output to the bus when the string output is equal to the highest voltage.
4. The system of claim 1 , wherein the respective converter is configured to receive power from the string output provided to the direct current input and generate a voltage at the direct current output that is connected in series with the string output.
5. A photovoltaic system, comprising:
a plurality of photovoltaic panels, wherein outputs of the plurality of photovoltaic panels are connected in series to provide a string output; and
a converter having a direct current input and a direct current output;
wherein the string output is connected to the direct current input of the converter to generate the direct current output; and
wherein the string output is connected in series with the direct current output of the converter to provide a predetermined voltage.
6. The system of claim 5 , wherein the predetermined voltage is connected to a parallel power bus.
7. The system of claim 6 , wherein a plurality of strings are connected via converters to the parallel power bus.
8. The system of claim 7 , wherein the parallel power bus is operated at the predetermined voltage that is equal to the string output of a strongest string of the plurality of strings.
9. The system of claim 8 , wherein the strongest string has a highest string output voltage among the plurality of strings.
10. A photovoltaic system, comprising:
a plurality of photovoltaic panels having outputs connected in series to provide a string output; and
a converter having a direct current input and a direct current output;
wherein the string output is connected to the direct current input to power the converter to generate the direct current output;
wherein the string output is further connected in series with the direct current output to provide a predetermined voltage onto a parallel power bus to which a plurality of strings are connected via converters; and
wherein the predetermined voltage is determined based on a string having a highest string output among the plurality of strings.
11. The system of claim 10 , wherein the parallel power bus is operated at the predetermined voltage equal to the string output of a strongest string of the plurality of strings.
12. The system of claim 10 , wherein the converter includes a bypass switch configured to provide a bypass path as the direct current output connected in series with the string output when the string output is equal to the predetermined voltage on the parallel power bus.
13. A method in a photovoltaic system, comprising:
connecting outputs of a plurality of photovoltaic panels in series to provide a string output;
providing a converter having a direct current input and a direct current output;
connecting the string output to the direct current input of the converter to generate the direct current output; and
connecting the string output in series with the direct current output of the converter to provide a predetermined voltage.
14. The method of claim 13 , further comprising:
connecting the predetermined voltage to a parallel power bus.
15. The method of claim 14 , further comprising:
connecting a plurality of strings via converters to the parallel power bus.
16. The method of claim 15 , further comprising:
operating the parallel power bus at the predetermined voltage that is equal to the string output of a strongest string of the plurality of strings.
17. The method of claim 16 , wherein the strongest string has a highest string output voltage among the plurality of strings.
18. The method of claim 17 , further comprising:
Identifying the highest string output voltage among the plurality of strings.
19. The method of claim 14 , further comprising:
operating a bypass switch of the converter to provide a bypass path as the direct current output connected in series with the string output in response to a determination that the string output is equal to the predetermined voltage on the parallel power bus.